Spectroscopic study of the I2 formation from the photolysis of iodomethanes (CHI3, CH2I2, CH3I, and CH2ICl) at different wavelengths

Cian Ping Tu, Hsin I. Cheng, Bor Chen Chang

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Abstract

Emission spectra following the photolysis of iodomethanes (CHI3, CH2I2, CH3I, and CH2ICl) at 266 nm were recorded in a slow flow cell. In addition to emission from the electronically excited species including CH (A2Δ, B 2Σ-, and C2Σ+), C 2 (d3Πg), and atomic iodine ( 4Po), a series of emission bands was observed in the 12 000-19 000 cm-1 region. The dominant structure of these emission bands was verified as the I2 B3Π+ 0,u-X1Σ+g emission at the 532 nm excitation, and the observed I2 was formed from collisions between iodine atoms generated from the C-I bond dissociation in these iodomethanes. The I2 emission spectra following the photolysis of CH 2I2 at different wavelengths were acquired, and the threshold energy for the first C-I bond cleavage was determined to be 208 ± 1 kJ mol-1. We also obtained the emission spectra of pure I2 at several visible excitation wavelengths for comparison with those from the photolysis of iodomethanes, and a least-squares global fit of the observed I2 emission bands yields more accurate anharmonicity parameters for the vibrational structure in the I2 B-X transition.

Original languageEnglish
Pages (from-to)13572-13577
Number of pages6
JournalJournal of Physical Chemistry A
Volume117
Issue number50
DOIs
StatePublished - 19 Dec 2013

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